The present invention relates to a turbine rotor formed by stacking disk shaped members in axial direction, and more particularly to a turbine rotor inserted heat resisting pipes by forming therein coolant flow passages in axial direction.
In general, a gas turbine in a thermal power generation plant is constructed with a compressor sucking an air (atmospheric air) and compressing up to a predetermined pressure, a combustor mixing the air compressed by the compressor with a fuel and burning for generating a combustion gas, and a turbine portion generating a driving force by expansion of a high temperature and high pressure combustion gas. Also, a gas turbine power generation facility is constructed by providing a generator converting the driving force generated by the turbine into an electric energy.
Amongst, the turbine portion is constructed with a turbine casing mainly housing the entire construction, a combustion gas flow path acting and flowing the combustion gas generated by the combustor, vanes and blades alternately arranged within the combustion gas flow path, and a turbine rotor formed by stacking turbine disks and spacer disks. The vanes are fixed on the inner periphery of the turbine casing and the blades are fixed on the outer periphery of the turbine rotor, respectively.
In the construction of the turbine portion, by flow of the high temperature combustion gas through the combustion gas flow oat, the turbine rotor is driven to rotate at high speed to generate the driving force (shaft rotating force). Accordingly, for obtaining high output by the gas turbine, it is an important point for elevating temperature of the combustion gas and for enhancing efficiency of the gas turbine at the entrance of the turbine portion.
Associating elevated temperature and enhanced efficiency of the gas turbine, it is essential to cool high temperature portion of the gas turbine, such as turbine blades and the combustion has flow path, for certainly attaining reliability of the gas turbine facility. Accordingly, particularly in the turbine blades, a blade cooling system is employed for protecting blade members from heat of the high temperature combustion gas flowing through the combustion gas flow path.
In the blade cooling system, there are some systems which use air extracted at a predetermined pressure from the compressor or a steam extracted from a steam turbine in a combined cycle power plant, development of which has been progressed in the recent years, is used as coolant. Such coolant is fed to each turbine blade through a coolant supply passage provided within the turbine rotor to cool the blades by flowing through the blade cooling path formed within each blade.
On the other hand, in such blade cooling system, as one type depending upon handling method of the coolant after cooling the blade, there is an open cooling system by directly discharging the coolant into the combustion gas flow path through slits or conduits formed in the blades. Since the coolant is discharged into the combustion gas flow passage after cooling the blade, the open cooling system causes lowering of the combustion gas temperature, mixing loss of the coolant and the combustion gas and lowering of performance of the turbine to lower efficiency of the turbine.
Accordingly, in order to improve efficiency of the gas turbine, in order to improve efficiency of the gas turbine, there has been proposed a closed cooling system, in which the coolant after cooling the blades is not discharged into the combustion gas flow path but is connected in the combustion chamber of steam turbine via a coolant recovery path provided within the turbine rotor.
As the conventional construction of the blade cooling system in such closed cooling system, there is a system disclosed in Japanese Patent Application Laid-Open No. Heisei 10 (1998)-220201, for example, in which coolant supply paths for supplying the coolant to the blades and coolant recovery paths for collecting coolant after cooling the blades (hereinafter, both are generally referred to as coolant flow path) are formed through the inside of the turbine rotor in axial direction, namely, provided perpendicularly intersecting with each disk shaped member and the stacking plane as mating surfaces of the disk shaped members.
On the other hand, in Japanese Patent Application Laid-Open No. Heisei 10-220201, there has been disclosed a construction for inserting the heat resisting pipes within the inside of the coolant flow paths with dividing per each disk shaped members. By this, thermal influence to each disk shaped member by flow the coolant can be reduced.
However, the following problems are encountered in the prior art.
In the construction of the turbine rotor as set forth above, the turbine disks carrying the blades on the outer periphery and the spacer disks disposed between the turbine disks are stacked, and a stacking bolt extends through perpendicularly to stacking planes. Even the coolant flow paths to flow the coolant, they are formed perpendicularly to respective stacking planes and extend therethrough. Accordingly, in relation to certainty of coupling of the turbine rotor and to sealing ability of the coolant flow paths, it is ideal in design that turbine disks and the spacer disks are tightly fitted with each other on the stacking planes without gaps.
However, when both of the coolant supply paths and coolant recovery paths are admixingly present in the turbine disks and the spacer disks, a temperature of the coolant in the coolant supply paths is about 250 C whereby a temperature absorbing temperature of the blade members is elevated as high as 500 C to cause thermal stress in the component members of the turbine disks and the spacer disks to cause non-uniform thermal deformation. This causes gaps in the stacking planes between the disk shaped members to be a cause of leakage of the coolant to the stacking planes. Due to leakage to the stacking planes, predetermined flow rate of coolant to the turbine blades cannot be certainly supplied to cause degradation of reliability and durability of the blade members.
The heat resisting pipes disclosed in Japanese Patent Application Laid-Open No. Heisei 10-220201 are for reducing thermal stress to be caused in respective disk shaped members due to temperature difference between the supply paths and the collecting paths of the coolant as set forth above. By inserting the heat resisting pipe having smaller internal diameter into respective coolant flow paths for reducing thermal influence to the external disk shaped member from the inside of the pipes.
On the other than, on the stacking surface, due to precision in production, since positions of forming the coolant flow paths between respective disk shaped members can be offset in circumferential direction and radial direction, it becomes necessary to make the external diameter of the heat resisting pipes small when single long heat resisting pipe is inserted through respective coolant flow paths. However, in the coolant flow paths in each disk shaped member, the gap is formed between the external diameter of the heat resisting pipe and the internal diameter of the coolant flow path. This gap may cause extra stress on the heat resisting pipe during operation to lower durability of the heat resisting pipe. Therefore, a problem is encountered in inserting single long heat resisting pipe. Furthermore, since the heat resisting pipe transports the coolant for cooling the blade, it is abruptly heated in comparison with each disk member to cause displacement of the heat resisting pipe in axial direction due to thermal elongation. Then, by centrifugal force developed by rotation of the rotor, the heat resisting pipe and the inner periphery of the coolant flow path contact to cause wearing in the heat resisting pipe due to displacement in the axial direction of the heat resisting pipe on the contact surface. As set forth above, when one long heat resisting pipe is installed, displacement of the heat resisting pipe in axial direction becomes large at the end portion thereof to increase wearing of the heat resisting pipe in the contacting surface with each disk shaped member. Increase of wearing can be a factor for decreasing life period of the heat resisting pipe. Accordingly, concerning the heat resisting pipe inserted into the coolant flowpath, a construction to insert with dividing per disk shape member is frequently employed as shown in FIG. 2 of Japanese Patent Application Laid-Open No. 10-220201 and so forth.
However, when the heat resisting pipe is inserted with divided per each disk shaped member, each heat resisting pipe inherently becomes small member to easily cause movement or rotation in axial direction or about axis in the heat resisting pipe per se during operating revolution of the turbine rotor to severe wearing and damage to be problem in durability.
On the other hand, in view of the precision in production, it is difficult to form the stacking plane with high flatness to completely eliminate the gap. Furthermore, even due to fluctuation of flatness of the stacking plane or fluctuation of tightening force of the stacking bolt, local gap in the circumferential direction is cased in the stacking plane between the turbine disk and the spacer disk. When even a little gap is formed, the coolant on the side of the supply path has higher pressure in comparison with the collection path side to cause leakage of the coolant from the supply path to the collection path for causing thermal unbalance in circumferential direction in the spacer disk. This thermal unbalance increases vibration of the rotor body.
When the heat resisting pipe is provided in divided form as set forth above, thermal stress and thermal deformation of the disk can be slightly reduced, it is not possible to prevent formation of the gap in the stacking plane due to fluctuation of flatness of the stacking plane or fluctuation of tightening force of the stacking bolt. Furthermore, as set forth above, each divided heat resisting pipes causes movement upon operating revolution of the turbine portion to cause leakage of the coolant into the gap in the stacking plane from joint portion of the divided heat resisting pipes to easily cause thermal unbalance.
On the other hand, the foregoing two problems, it is required to provide a structure for fixing each heat resisting pipe and a structure for preventing leakage of the coolant per each stacking plane. However, when these structures are provided individually, the processing portions on the surface of each disk surface is increased to be complicate shape to easily cause concentration of stress to be not desirable in view point of strength.
A first object of the present invention is to provide a turbine rotor which can fix the heat resisting pipes provided in divided form per the disk member with simple structure for preventing wearing and damaging.
A second object of the present invention is to provide the turbine rotor which can minimize leakage of coolant to the stacking plane by using the fixing structure of the heat resisting pipe.
In order to accomplish the first object, according to the first aspect of the present invention, a turbine rotor comprises: a coolant flow path formed through a plurality of disc shaped members respectively stacked across stacking planes in axial direction; a heat resisting pipe divided into a plurality of fractions adapted to be inserted into a portion of the coolant flow path defined in each disc shaped member; spot facing recesses each formed at opening portion of coolant flow path at the same side of the disc shaped member coaxially with the coolant flow path and having greater inner diameter than the opening portion; and ring shaped projecting portions formed at respective end portions of the fractions of the heat resisting pipe and engageable with respective spot facing recesses.
By providing the spot facing recess in the opening portion of the coolant flow path, and by providing the ring shaped projecting portion engageable with the spot facing recess at the end of the heat resisting pipe for engaging with the spot facing recess to be restricted movement in diametrical direction. Also, the ring shape projection is sandwiched by two disk shaped members. Therefore, even during operating revolution of the turbine rotor, the heat resisting pipe is fixed in diametrical direction and axial direction to prevent wearing and damaging.
In the construction set forth above, it is preferred that each of the ring shaped projecting portions is formed with a cut-out step portion on the side of the stacking plane for receiving therein an annular seal member.
By providing special machining for the disc shaped member, for providing the seal structure exclusively using the fixing structure on the side of the heat resisting pipe, increasing of stress concentration by machining can be avoided and leakage of the coolant from the coolant flow path to the stacking plane can be reduced.
Preferably, a material of the heat resisting pipe has greater linear thermal expansion coefficient than that of a material of the disk shaped member.
By this, during high temperature state in operation of the turbine portion, the heat resisting pipe causes thermal expansion to be elongated in axial direction in greater magnitude than the disc shaped member. By this, the annular seal disposed between the ring shaped projecting portion and the stacking plane mating to the former is compressed to increase sealing performance to minimize leakage of the coolant.
It is further preferred that at least two projecting ridges are provided on outer periphery of the ring shaped projecting portion, and back facing grooves engageable with the projecting ridges are formed on the inner periphery of the spot facing recess at circumferential positions corresponding to positions of the projecting ridges.
By this, the heat resisting pipe is fixed in circumferential direction to prevent wearing and/or damaging.
Also, in the preferred construction, engaging projecting portions having smaller inner diameter than that of the coolant flow path is formed the end of the heat resisting pipe on opposite side of the end where the ring shaped projecting portion is provided, the engaging projecting portions is located in an opening portion of the coolant flow path on the stacking plane of the disc shaped member on opposite side of the stacking plane where the spot facing recess is formed.
By this, even when crack is formed in a part of the heat resisting pipe to result in rapture, the separated piece or debris is prevented from loosing off for avoiding unbalance vibration due to offset of the gravity center of the disc. On the other hand, damaging of other member by loosed off debr4is can be prevented to improve reliability.
According to the second aspect of the present invention, a turbine rotor comprises: a coolant flow path formed through a plurality of disc shaped members respectively stacked across stacking planes in axial direction; a heat resisting pipe inserted through the coolant flow path; a ring shaped projecting portion provided on the heat resisting pipe; and a hole portion provided in the coolant flow path at a stacking plane of the disk shaped members and engageable with the ring shaped projecting portion at the end of the heat resisting pipe.
According to the third aspect of the present invention, an assembling method of a turbine rotor comprises the steps of: forming a coolant flow path through a plurality of disc shaped members respectively stacked across stacking planes in axial direction; inserting a heat resisting pipe in the coolant flow path; providing a ring shaped projecting portion in the heat resisting pipe; providing a hole portion in the coolant flow path on the stacking plane of the disc shaped member; and inserting the heat resisting pipe into the coolant flow oath with engaging the ring shaped projecting portion of the heat resisting pipe with the hole portion.
According to the fourth aspect of the present invention, a cooling method for cooling a high temperature portion of a gas turbine comprises the steps of: forming a coolant flow path through a plurality of disc shaped members respectively stacked across stacking planes in axial direction; inserting a heat resisting pipe in the coolant flow path for flowing a coolant through the coolant flow path; providing a ring shaped projecting portion in the heat resisting pipe; providing a hole portion in the coolant flow path on the stacking plane of the disc shaped member; and inserting the heat resisting pipe into the coolant flow oath with engaging the ring shaped projecting portion of the heat resisting pipe with the hole portion whereby for flowing coolant through the coolant flow path.